Dental health research requires not only clinical studies on preventive and restorative care, but also systematic growth in our basic understanding of the anatomy, physiology and behavior of orofacial systems. Continued basic research is essential, ranging from systems analysis of normal structure and function to investigation of the processes of adaptation following disease, aging or dental treatments. A critical aspect of this inquiry is our understanding of the neural control of rhythmic or complex mouth movements such as chewing or speaking. While animal models of speaking movements have obvious limitations (and, in humans speaking and masticatory movements are controlled differently), a number of models exist for studying the sensory, motor, neural and adaptive bases of mastication in animal preparations. Mastication is one neurobehavioral system that is affected by aging and disorders such as temporo-mandibular joint malfunction, stroke, Huntington~s and Parkinson's diseases, and difficulty adapting to dental implants. Advancements in our basic knowledge of jaw movement control systems will suggest and improve treatments for these and other disorders. The specific aims of this project are: (1) to examine the relationships between limbic and motor neural responses and the development of adaptive jaw movements in awake, undrugged rabbits. (2) to differentiate the impact of aging on reflexive and conditioned jaw movements by comparison of the movements exhibited by young and old rabbits, as well as examination of the dynamics of each subject~s adaptation to the timing required for successful performance. (3) to evaluate the impact of aging on neural responses in forebrain and brainstem that contribute to the performance and adaptation of masticatory responses. These aims will be addressed in the context of recording neural and behavioral activity simultaneously during jaw movement training in rabbits. Classical conditioning of rhythmic jaw movements has been developed as a model system for evaluation of the neural bases of reward learning. It is a very well controlled form of adaptive behavior that facilitates discrimination among sensory, motor, motivational and cognitive processes involved in ongoing behavior. If we can document the sensitivity of this paradigm to variables such as aging, it may become a widely applicable behavioral model.